1.192.1 SystemExceptions.WrongClass class: signaling

signalOn: anObject mustBe: aClassOrArray

Raise an exception. The given object should have been an instance
of one of the classes indicated by aClassOrArray (which should be
a single class or an array of classes). Whether instances of
subclasses are allowed should be clear from the context, though
in general (i.e. with the exception of a few system messages)
they should be.